1. Field of Invention
The present invention relates generally to accessory apparatus for use with a plain bearing located in a housing and slidably positioned on a shaft or guide member. More particularly, the invention relates to apparatus adapted for adjusting the running clearance between the bearing and the shaft, and for optionally provide a frictional drag and/or braking force between the bearing and shaft; and which, while suitable for other uses, is particularly useful in connection with adjusting the running clearance and/or braking linear slides provided with plain bearings sliding on a guide rail.
2. Description of Prior Art
Plain bearings are often used for either slidably or rotatably supporting a shaft member in a stationary housing, or slidably or rotatably supporting a housing member on a stationary shaft. In such arrangements, it is desirable at times to stop the relative motion between the housing and the shaft, or to provide a frictional drag to resist the relative motion. At present, suitable friction and braking apparatus may be embodied in a separate unit, or may involve a clutch or conventional braking arrangement, and may be relatively complicated and expensive. Thus, there is a need for a simple, relatively inexpensive means for applying a frictional drag between the bearing and shaft, and for optionally applying sufficient friction to act as a braking force.
It is also well known that plain bearings have a limited life as a result of wear. Bearings are installed with an initial shaft clearance which tends to increase from extended use. Accommodation of an acceptable level of wear is typically taken into account in design of any particular arrangement, and the bearing is then typically replaced when the wear exceeds an allowable limit. It is apparent that a simple, relatively inexpensive apparatus adapted to adjust the clearance between the bearing and shaft, to accommodate wear and prolong the useful life of the bearing, would reduce bearing replacement costs, and in many instances, reduce the overall long-term cost of operation.
One common use for plain bearings is in connection with linear slides. A typical linear slide arrangement includes a stationary shaft or other stationary guide rail, and a housing slidably positioned on the guide rail with one or more plain bearings. For example, Komiya, U.S. Pat. No. 5,297,873 discloses a linear motion slide with generally rectangular guide rail and a separate slide stop assembly.
Osawa, U.S. Pat. No. 4,941,758 discloses a linear slide and guide rail arrangement in which the slide housing is provided with a slit defining outer and inner side wall portions, and a pressing bolt adapted to elastically deform the inner wall portion for adjusting the gap between the bearing and the guide rail. While the Osawa arrangement is an improvement for certain arrangements over the prior art, a simpler arrangement which avoids the need to form the slotted sidewall, but which is adapted to adjust the clearance between the bearing and shaft is desirable to further reduce the cost of clearance adjustable sliders.
From the foregoing, it is clear there is a need for a simple, and relatively inexpensive arrangement adapted to adjust the clearance between a plain bearing and associated shaft, and which is further adapted to apply a frictional drag and optionally a braking force between the bearing and the shaft.